Is It Hotter by the Slide? A Schoolyard Temperature Investigation

Every child has an opinion about where the schoolyard is hottest. “By the slide!” “In the sunny corner!” This is a chance to replace opinions with measurements, and to find out how hard a fair measurement is.

The question

“Where is the warmest spot in the schoolyard, and why?” Differences in temperature between places that are close together are called microclimates.

What you need

A thermometer for each team (outdoor dial, liquid-in-glass with a plastic back, or cheap digital)
A small card taped over the thermometer as a sun shade
A metre stick or a 1 m string
A clipboard and pencil
A stopwatch or phone timer

Plan a fair measurement

Students often forget to plan, so spend time here. Ask: “If two teams measure the same place and get different numbers, why?” Possible answers:

One held the thermometer in sunlight and the other in shade.
One held it at ground level and the other at head height.
One read it right away and the other waited.
They used different thermometers.

Decide the rules together:

Same height: 1 m above the ground, measured with the string.
Shaded bulb: the card keeps direct sun from heating the sensor itself.
Same wait: hold the thermometer still for 2 minutes before reading.
Same time: all teams measure within the same 10-minute window.
Record the place, the time and the temperature.

Choose spots to compare

In the sun on grass
In the shade of a tree
Beside a brick wall
On asphalt or by the slide
Near a door or in a sheltered corner

Predict the order from warmest to coolest before going out.

What usually happens

Dark, hard surfaces such as asphalt and metal slides absorb sunlight and warm the air above them. Shaded spots and grass tend to be cooler, because plants shade the ground and release water vapour, which cools. Brick walls store heat and release it slowly. Wind can even out differences. Results depend on the day, so compare data across several days, if you can.

If your thermometer is placed on a hot surface, you’re measuring the surface, not the air. Say so, and ask how you’d measure surface temperature properly.

Explain the differences

Use evidence: “The asphalt spot was 4 °C warmer than the grass spot. Dark surfaces absorb more sunlight than light surfaces, and grass loses heat as its water evaporates.” If the data surprises you, say what you’d check next.

Safety

Keep thermometers off hot surfaces that could burn, stay away from roads, wear sun protection and stay together as a group.

The activity is Is it hotter by the slide? from Weather Detectives, which also covers Why does a chinook feel like spring in January? and Why do farmers care about the last frost? Younger students can try Which way is the wind blowing? Sign up for three lessons free.